that's a really tough situation and i don't really know what you want to hear...but what i will say is that the worst thing in life (as you have realized) is regretting something. that being said, i think that if you two really do love each other, you should try to make a relationship work. i know there is another man involved but if he is being unfaithful it doesn't sound like he is too happy in the relationship, and perhaps he would just bow out when/if he is confronted about his cheating ways and his wife's feelings for another person (you). The fact that there is a child involved further complicates things, but that is a whole other issue that can be dealt with later down the road. i don't really know what else i can say... hopefully someone else has been in a similar postion to you and can offer some better insight.

all the best

*love*